This invention relates generally to vapor compression refrigeration systems, and more particularly to a vapor compression refrigeration system having means for interjecting relatively cool liquid refrigerant into evaporated refrigerant prior to the compressor of the system.
Vapor compression refrigeration systems generally comprise a compressor, a condenser, an expansion device, and an evaporator connected by appropriate refrigerant lines to form a refrigeration circuit. Refrigerant vapor is compressed by the compressor and fed to the condenser where the refrigerant releases heat to a cooling medium and condenses. The condensed refrigerant then flows through the expansion device where the pressure and temperature of the refrigerant are reduced. From the expansion device, the refrigerant passes into the evaporator, absorbs ambient heat, and vaporizes. Vaporous refrigerant is then drawn back into the compressor completing the circuit.
Refrigeration systems of the foregoing type are frequently cycled on and off to produce a heat transfer medium having a generally uniform temperature or to maintain a desired temperature in a room or building. This type of control, however, often produces undesirably wide temperature fluctuations. To provide a more uniform temperature it has been proposed heretofore to control the cooling capacity of this type of refrigeration system by throttling the flow of refrigerant from the evaporator to the compressor. By throttling refrigerant passing to the compressor, the refrigerant flow rate through the entire refrigeration system can be varied. The amount of refrigerant passing through the evaporator can be regulated to control the amount of heat absorbed thereby. In this manner, the refrigeration system may provide a heat transfer medium having a substantially constant temperature despite changes in the cooling load of the heat transfer medium.
Compressors of the above-described refrigeration systems often comprise a hermetically or semi-hermetically sealed casing enclosing a vapor compression means and an electric motor for driving the compression means. Refrigerant returning from the evaporator is directed into the casing for compression, and this refrigerant cools the compressor, and more important the windings of the electric motor. When refrigerant is throttled prior to entering the compressor, the refrigerant may be unable to sufficiently cool the motor windings, causing overheating thereof. This may endanger the components of the compressor, particularly the motor, or the overheating may activate various safety switches, rendering the compressor motor and, hence, the refrigeration system inoperable.